Wafer inspection usually includes illuminating a wafer by illumination optics and then collecting and detecting light scattered or reflected from the illuminated wafer. The detection can be performed by one or more sensors to provide one or more detection signals that are then analyzed in order to detect defects.
Wafer inspection methods and systems can differ from each other by their light collection and detection techniques. Bright field inspection systems and methods collect light that is reflected (according to Snell's law) from the illuminated wafer while dark field inspection systems and methods collect light that is scattered from the illuminated wafer. Wafer inspection tools may use imaging or non-imaging detectors. Imaging detectors may include CCD sensors while non-imaging detectors may include PMT detectors.
There is a growing need to increase the throughput of wafer inspection systems, to increase their sensitivity, to enhance type of information that can be generate from a wafer inspection tool, while reducing the cost of these wafer inspection tools or at least reducing the cost of an inspection of a wafer.
Different wafer inspection systems provide different solutions to the above-mentioned contradicting demands. There is a need to provide efficient wafer inspection systems that are capable of providing size information.